That rack support was purchased in fall '76 - early '77 from Bike Warehouse (later Bike Nashbar, and later just Nashbar)...I don't think it had any particular branding. Also bought from Bike Warehouse was the Zefal HP frame pump, SunTour barcons, ALE handlebar-mount water bottle cage, TA bottle, Cannondale 'Toot' seat bag....Lots of stuff that winter! Later that spring the bike was treated to Phil hubs, stainless butted spokes, and somebody's narrow clincher rims... That self-built wheelset lasted the bulk of the old Fuji's miles - some 30k miles over the next few years... Rear wheel was tacoed after an unexpected (inattention) slip off the pavement and a 5-6" drop off the pavement to the gravel and my poor attempt at recovery...